Abstract: The study investigates whether: (1) measures of anger and aggression will correlate with processing time of angry material and with generation of aggressive responses and (2) tryptophan challenge in people abstinent from methylenedioxymethamphetamine (MDMA) and controls will affect angrycognitivebias. Thirty-two current MDMA users abstinent for 3 weeks, 32 ex-users abstinent for longer than 1 year and 32 non-MDMA substance users were recruited. Trait measures were administered before and state measures before and 5 h after an amino acid drink, depleted or augmented with tryptophan. After the drink, subjects undertook a computer task, which involved reading ambiguous short stories. Reading times to a key sentence describing an angry or non-angry reaction were recorded and subjects wrote a continuing sentence for half the stories. Subjects were faster to process angry than non-angry reactions, indicating the presence of angrycognitivebias. Trait anger and aggression were correlated with processing time of angry relative to non-angry reactions, particularly in the current users. Impulsivity was correlated with non-specific speed of response. Evidence of angrycognitivebias was shown in this group of substance users, which was not specific to MDMA use. (PsycINFO Database Record (c) 2004 APA, all rights reserved)